I have a 50 in full champion, 3 level 25s, and like 6 level 15s. I havent exploited anything, got to 50 the beginning of the second week after early access and barely played during early access. A tip that helps leveling characters alot is to do the dailes, they give you lots of xp.
(PvP daily, space dailies, flashpoint dailies) all give very good xp.
I pay attention to all the class stories as well.